Android prefers to have RAM full. It makes loading apps faster with less battery drain. The version of Android that came with the Droid 4 was pretty bad with memory management. This is no longer the case with anything 4.1 and above.
The Note 4 i believe has a recents button that you can swipe away apps still in memory.
Press the recent apps button (the button to the left of the home key). You can swipe away apps there. I wouldn't worry about RAM though as it does not effect performance on Android, especially on power houses like the Note 4.